Research on the Relationship between the Thickness of the Hard Strata and the Roof Caving Hidden Danger Level

In order to find out the cause of the mining roadway of mine test roof fall in the excavation period, to based roof stability partition method, The main research methods is using RFPA software numerical simulation, according to the specific condition roof strata of the mine test, build 6 different thickness of medium sandstone model, get the corresponding characteristics of roof deformation and roof caving hidden danger level. The results of the study show that under the condition roof strata of the mine test, At the stratigraphic horizon is certain, Thickness decrease of medium sandstone is the main cause of roof fall, when the thickness of medium sandstone less than 1.5m,the roof is unstable, roof caving hidden danger level depend on its upper strata; 1.5m is constant critical value of roof caving hidden danger level, the middle of roadway have be deformation, but articulate between rock block can also keep the roadway stable; when the thickness of medium sandstone more than 1.5m, it can be loading layer, roof caving hidden danger risk is low, the type rock is Ⅰ level, the roadway is basically never collapse.